1. Field of the Invention
The present invention relates to a print head that ejects ink and an inkjet printing apparatus, and more specifically relates to a structure for cooling a print head or adjusting temperature of the print head.
2. Description of the Related Art
Conventionally, the inkjet printing apparatus using a print head that ejects ink is provided at a low running cost and is capable of being miniaturized, and therefore, has been widely used to output information of a computer apparatus and the like, and has been commercialized.
In recent years, it has been desired to obtain a print head having a longer printing width (a length of an ejection opening array) in order to achieve printing of higher resolution image at higher speed. Specifically, the print head having the ejection opening array length of 4 to 13 inches has been desired.
Thus, an increase in length and density of the ejection opening array in the print head enhances energy applied to the print head and results in a remarkable temperature rise of the print head during printing. As a result, there occurs a problem such as an increase in variation in an amount of ejection for each page, degradation in printing property for continuous printing, and the like.
Conventionally, in Japanese Patent Laid-Open No. 8-276575 (1996), Japanese Patent Publication Nos. 2656834 and 2744475, as a structure that deals with a temperature change of the print head, proposed is one in which a heat pipe and a heat releasing member are provided to a print head to cool the print head or equalize the temperature thereof.
However, the structure, described in Japanese Patent Laid-Open No. 8-276575 (1996) and the like, in which the print head is cooled or the head temperature is equalized, provides insufficient efficiency in some cases. More specifically, in the conventional structure, the heat pipe and the heat releasing member are later fitted on or externally fitted to the completed print head, causing a problem in which a distance between a printing element substrate, which is a heat source in a print head, and the heat pipe cannot be reduced sufficiently. Moreover, later fitting the heat pipe on the print head sometimes causes a problem that a contact area between the heat pipe and the print head is limited.
As described above, the conventional cooling or temperature-equalizing structure, in some cases, may provide low efficiency in cooling the print head or equalizing the head temperature, that is, may provide insufficient function. Even in the conventional structure, satisfactory effects of cooling and temperature equalizing are obtained depending on the printing condition. However, particularly when a continuous printing property is intended to be improved with the print head having an increased length and density of the ejection opening array, there is a possibility that printing defects (density unevenness and non-ejection of ink due to bubbles) due to a temperature unevenness and a temperature rise of the print head cannot be suppressed.